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Breakaway Switch Diagram for Installation on a Dump Trailer with Trailer Mounted 12 volt Battery


I have a loudo dump trailer that has a battery in it. There are 4 wheels and electric brakes. The black wire from the harness connects to electric brake on the truck goes to one wire on each of the four brakes. The red wire goes to the other wire on the electric brakes. The red wire connects to the vehicles + power. Off of this wire there is a splice that goes to a breakaway switch out of this switch goes to the + power on the onboard trailer battery. The brakes do not work. Before I do it can you tell me if im doing this correctly. Take the black wire and splice it into the breakaway switch and then to the + power on the trailer while keeping it connected to the brake lead on my truck . Take the red wire and connect it to the - on my truck. I will then take a new wire from the + on the truck and run it straight to the battery to charge it. Hope you can help me. I am not familiar with trailer electric brakes and from what I gathered from your video and diagrams there should be no reason why the trailer is wired the way it is. I want to be 100 sure so that I do not damage the magnets. Also, the + lead out of the 7 point connect has never been on a vehicle that supplied power so there is no way that the magnets got 2 different positive volts at the same time. I did verify that my 7 pin connector is working correctly.

Expert Reply:

I attached a diagram showing how a breakaway switch, like part # 420000, would be wired to a trailer mounted battery like the one on your Loudo dump trailer.

With this type of setup you would not want to pull the breakaway switch with the trailer connected to the vehicle, to avoid a short circuit situation which could damage your brake controller. When testing the breakaway switch just be sure to disconnect the trailer connector from the truck, as it would be in a breakaway situation.

The wiring you mentioned sounds like the magnets on your trailer are connected to the brake controller output circuit and the 12 volt power circuit on the trailer. This situation is incorrect and if you ever attached the trailer to a vehicle with power on the 12 volt circuit at the 7-Way you would have a short circuit situation as you have noted. Each brake magnet should have one wire grounded and one wire connected to the brake controller output as seen in the diagram. Brake magnets are not polarity sensitive so it does not matter which wire you ground and which wire you connect to the brake controller output circuit.

If you follow the diagrams for a 7-Way connector on our wiring page, see link, and make sure your vehicle is wired the same way, you should be able to get things wired up. Let me know if you have any other questions.

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expert reply by:
Robert G

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